Install underfloor heating one after another

Hello everyone,
the following situation: We have moved into a relatively old house which we are now renovating step by step. The house is already habitable, as I said, we are already living in it. Now, among other things, the heating system needs to be renewed.
Basically, I am in favor of a heat pump, but then I would also have to replace the radiators. Of course, underfloor heating would be best, but since we are already living here and it would be financially somewhat difficult to do everything at once, I would like to install underfloor heating room by room one after the other and only later connect them step by step. Is that basically feasible?
The question would also be, are there coupling systems to route the pre-installed connections from the last room to the heating system in the end?
Thanks for your answers!

Well, welcome to the club. That’s exactly what we are planning too, just without an old existing heating system and therefore no radiators either. Previously, there were night storage heaters installed; those stoves were the first to go. We also considered a heat pump but discarded it due to unpredictable electricity costs. Instead, we installed a heat pump air conditioning system that can heat and ventilate, but we did not plan it as the standard heating. However, it was wonderful in the summer...

Back to the topic. Since our renovation budget was small (60,000 for complete renovation), we ultimately decided on a pellet boiler with a buffer tank. The total cost was 6,000 euros including installation and pipes (there were none), and we received half of that as a grant from BAFA, which obviously worked out very well for us.

The underfloor heating was already a bigger problem because we simply couldn’t find anyone who would install it room by room. We received a few offers, but they required at least 100 sqm to be done at once, which we couldn’t afford as it is difficult to clear 100 sqm in an inhabited house, it was just not possible; 30 sqm was the maximum. And nobody wanted to do that. Accordingly, we have now ordered the underfloor heating as a dry construction system (in my opinion, nothing else is possible in an old building anyway; who wants to pour liters of water into a closed house?) from selfio and are now installing it ourselves. The connection of the distributor to the buffer tank will then be done by a company again, ideally the same one that installed the boiler. But we won’t ask them before the underfloor heating is laid; that makes no sense since, from experience, it will take me forever to prepare the floor – we have broken out the screed, renewed the sealing, carried out a leveling with sand, laid insulation boards, and on top of that OSB. The system panels of the underfloor heating are to go on that. The tightness test will also be done by the company. I don’t know if I can manage all that so easily, but after 3 years of searching for someone to install the underfloor heating, the only options left were either to permanently do without heating and leave the installed system idle or to install the underfloor heating ourselves, which I have never done before. Allegedly, it is supposed to be very easy, well, I’ll be surprised. At least it was cheap. For 100 sqm, it was 1,000 euros for the pump, distributor, connection parts, and supply pipe (no idea if that will be used later, otherwise it can also be used for the water pipes). And about 2,000 euros for system panels, piping (aluminum composite, the most expensive in the offer), foil, edge insulation strips (which we actually don’t need but bought anyway), and heat-conducting plates. In addition came the costs for the dry screed, I think 15 euros/sqm.